1. Field of the Invention
The present invention relates to an ion implantation method, an SOI wafer manufacturing method and an ion implantation system.
2. Description of the Related Art
In a field of IC devices, a method for implanting predetermined ions in a semiconductor substrate has conventionally been used when a transistor junction is formed.
Ion implantation is also used in a smart cut method which is one of the manufacturing methods of silicon-on-insulator (SOI) wafers (Japanese Patent Laid-Open Publication No. 2000-12285, etc.). According to the smart cut method, an SOI wafer is manufactured by implanting hydrogen ions in a Si substrate through an insulating layer (SiO2 layer or the like) formed on a surface of the Si substrate, bonding this substrate to another Si substrate and then cutting it at a hydrogen ion implanted layer.
The ion implantation is normally carried out by using an ion implantation system. For an ion source of the ion implantation system, an arc discharge ion source which employs a hot cathode is generally used. With the ion source of this type, it is relatively difficult to generate high-density plasma only by electric arc discharge. Therefore, by forming a magnetic field in a direction penetrating a plasma chamber along the cathode (i.e., orthogonal to an ion extraction direction), plasma generation is promoted and a beam current of extracted ions is improved.
Recent miniaturization and high performance of IC devices have brought about an accelerated reduction in energy of implanted ions. For example, in implanting boron (B), ion energy is required to be less than 1 keV.
However, if ions are implanted by using the above-mentioned conventional ion implantation, the beam current, which is necessary for the ion implantation, is reduced. This beam current reduction tends to occur especially when light (i.e., small mass number) ions or low-energy ions are implanted. Therefore, in processes of forming a transistor junction, an ion implanted layer of an SOI wafer and the like, which require high-dose ion implantation, ions cannot be implanted with proper throughput.